The Fluctuation-Dissipation Theorem fails for fast superdiffusion

We study anomalous diffusion for one-dimensional systems described by a generalized Langevin equation. We show that superdiffusion can be classified in normal superdiffusion and fast superdiffusion. For fast superdiffusion, we prove that the Fluctuation-Dissipation Theorem does not hold, which induces an effective temperature in the system. This effective temperature is a signature of metastability found in many complex system such as Spin-Glass and granular material.